RAVAN: CubeSat Demonstration for Multi-Point Earth Radiation Budget Measurements

Area of Science:

• Earth Science
• Climate Science
• Materials Science

Background:

• Accurate measurement of Earth's radiation budget is critical for climate change prediction.
• Existing technologies for radiation measurement are costly, limiting constellation-based monitoring.
• The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) mission aimed to address these limitations.

Purpose of the Study:

• To demonstrate the viability of vertically aligned carbon nanotubes (VACNTs) as broadband absorbers in radiometers for Earth radiation measurements.
• To test gallium phase-change black body cells as stable references for on-orbit sensor calibration.
• To assess the performance and stability of VACNT-based radiometers compared to traditional cavity radiometers.

Main Methods:

• The RAVAN 3U CubeSat carried two VACNT and two cavity radiometers, along with gallium black body calibration cells.
• The CubeSat performed routine solar and deep-space attitude maneuvers for calibration.
• Data was collected over 20 months in a Sun-synchronous orbit.

Main Results:

• VACNT radiometers demonstrated excellent long-term stability and high correlation with cavity radiometers.
• Gallium black body cells provided a repeatable calibration standard, despite one unit failing.
• Short-term variability and VACNT-cavity biases (3% Total, 6% SW) were identified as challenges for future missions.

Conclusions:

• RAVAN successfully demonstrated VACNT technology as a promising, compact, and sensitive alternative for Earth radiation budget measurements.
• The mission highlighted the need for improved thermal control and bias correction in future CubeSat radiometer designs.
• VACNT technology shows potential for cost-effective, multi-point constellation measurements crucial for climate monitoring.